1. Field of the Invention
This invention generally relates to tactile input devices and more specifically to tactile input devices with integral touch input surfaces.
2. Description of Related Art
Tactile input devices are becoming more popular in a variety of applications. Cellular telephones, personal digital assistants (PDAS) and other electronic devices seek to incorporate greater numbers of functions in such devices for a given volume. Tactile input devices can provide this capability. This has led to a number of approaches for providing input devices that utilize capacitive, resistive, strain gauge and other types of sensors.
For example, U.S. Pat. Pub. No. 2007/0257821 to Son et al. (assigned to the same assignee as the present invention) and granted on Oct. 27, 2009 as U.S. Pat. No. 7,609,178 discloses a reconfigurable tactile sensor input device. The input device uses capacitive sensing and includes a first rigid electrode layer, a compressible dielectric structure and a second flexible electrode layer. The dielectric structure may include a matrix of compressible geometric elements with voids therebetween. This approach provides an individual with varying levels of tactile force sensing. An optional flexible display may be mounted over the input device to indicate the present configuration to the individual, which configuration can change from time to time based upon various inputs.
U.S. Pat. Pub. No. 2007/0242037 to Son (assigned to the same assignee as the present invention) and granted Sept. 29, 2009 as U.S. Pat. No. 7,595,788 discloses an electronic device housing with an integrated user input capability. This device measures the force level applied by the individual to a housing for an electronic device. A capacitive sensor is formed between a conductive inside surface of the housing and an electrode on a rigid base. The application of force to the housing deflects a corresponding portion thereby to change the capacitance across the sensor.
In addition to the developments such as those described above, efforts have also been directed to the development of touch location devices, such as touch screens. U.S. Pat. No. 7,148,882 to Kamrath et al. discloses a complex to build capacitor-based force sensors that detect a difference caused by an applied force over a continuous range of applied forces that includes a zero force. A number of these sensors are distributed under an input structure. When a force is applied, the forces as measured by the capacitance properties of each sensor are converted into the position of the applied force on the input structure.
U.S. Pat. No. 7,183,948 to Roberts discloses a tangential force control touch location device that includes force sensor principal elements, lateral softening means and preload springs. A mechanical path, that does not include the force sensors, comprises a plurality of shunt connections that constitute the lateral stiffening means for impeding lateral motion of the touch surface.
Each of the foregoing references discloses different approaches. Manufacturers who wish to incorporate a touch screen with a tactile input device such as shown in the above-identified patent publications purchase the input device from one vendor and the touch screen device from another vendor. Then the manufacturer must determine an approach for integrating the two. Generally the electronics associated with each component are not compatible, so different processing approaches must be undertaken. This may further increase the price and size of the input device to accommodate the different circuits in the device or require more complex signal transfers to external electronic and processing components.
What is needed is a tactile input device that provides a touch screen display in combination with various keyboard configurations whereby the cost of the device is minimized and electronic processing by the device minimizes the communications required with external devices. What is also needed is a universal input solution where one controller IC can handle a touch screen as well as a multi-touch input keypad and specialty buttons such as a pressure sensitive scroll side button.